Remove unused branch triggers.

The scheduled beta trigger and the poller stable trigger do not trigger
any jobs. This can't be generated natively by lucicfg, so remove the
triggers. stable-gitiles-trigger-scheduled was renamed to
stable-gitiles-trigger to match what will be generated by starlark.

Bug: 1011908
Change-Id: I9827d933c8b92c78ab4a44a3ca4b2a883b00875a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031185Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736934}

infra/config/generated/luci-scheduler.cfg

@@ -470,18 +470,6 @@ trigger {
   triggers: "ci-beta-linux-chromeos-rel"
 }
 
-trigger {
-  id: "beta-gitiles-trigger-scheduled"
-  acl_sets: "default"
-
-  schedule: "0 7 * * * *"  # Once per day at 7 AM UTC (11 PM PST)
-
-  # A task must be defined
-  noop {}
-
-  # TODO(gbeaty) Move builders to beta-gitiles-trigger as they are made green
-}
-
 ################################################################################
 # Stable branch
 
@@ -489,18 +477,6 @@ trigger {
   id: "stable-gitiles-trigger"
   acl_sets: "default"
 
-  gitiles: {
-    repo: "https://chromium.googlesource.com/chromium/src"
-    refs: "refs/branch-heads/3945"
-  }
-
-  # TODO(gbeaty) Move builders from stable-gitiles-trigger as they are made green
-}
-
-trigger {
-  id: "stable-gitiles-trigger-scheduled"
-  acl_sets: "default"
-
   schedule: "0 9 * * * *"  # Once per day at 9 AM UTC (1 AM PST)
 
   # A task must be defined

infra/config/luci-scheduler.cfg

@@ -470,18 +470,6 @@ trigger {
   triggers: "ci-beta-linux-chromeos-rel"
 }
 
-trigger {
-  id: "beta-gitiles-trigger-scheduled"
-  acl_sets: "default"
-
-  schedule: "0 7 * * * *"  # Once per day at 7 AM UTC (11 PM PST)
-
-  # A task must be defined
-  noop {}
-
-  # TODO(gbeaty) Move builders to beta-gitiles-trigger as they are made green
-}
-
 ################################################################################
 # Stable branch
 
@@ -489,18 +477,6 @@ trigger {
   id: "stable-gitiles-trigger"
   acl_sets: "default"
 
-  gitiles: {
-    repo: "https://chromium.googlesource.com/chromium/src"
-    refs: "refs/branch-heads/3945"
-  }
-
-  # TODO(gbeaty) Move builders from stable-gitiles-trigger as they are made green
-}
-
-trigger {
-  id: "stable-gitiles-trigger-scheduled"
-  acl_sets: "default"
-
   schedule: "0 9 * * * *"  # Once per day at 9 AM UTC (1 AM PST)
 
   # A task must be defined